Those shocked by the Flint water crisis should prepare themselves for even worse news: An investigation by Reuters of lead testing results across the country has found almost 3,000 areas with poisoning rates far higher than in the Michigan city.

The affected communities uncovered by Reuters extend from Warren, Pennsylvania, where 36 percent of children tested had elevated lead levels, to an area of Goat Island, Texas, where 25 percent of tests revealed poisoning. In some neighborhoods in distressed cities like Baltimore, Cleveland and Philadelphia, the rate of high tests over the past decade ranged from 40-50 percent.

As in Flint, legacy lead in the form of paint, plumbing or industrial waste has been the root cause of the poisoning. And because many of the most impacted zones lie in poor rural communities, forgotten post-industrial cities or largely minority neighborhoods, the problem has been left to fester for decades by the very authorities that have been charged with protecting public health. Perhaps the worst tragedy in this crisis, which appears to be emerging at a national level, is that disadvantaged children are those who are most likely to have been poisoned.

Reuters' is not the only investigation of the national water crisis to come out, but the question we have to ask ourselves remains: How did this happen in the first place?

As it turns out, the real culprits in this crisis have come in the forms of insufficient funding, ill-conceived austerity, sheer incompetence and private greed - in short, lack of government oversight or accountability. Reuters found it was insufficient resources that stymied efforts to enact proper testing and poisoning prevention measures.

While political leaders have justifiably blamed the US Environmental Protection Agency (EPA) and state regulators for dawdling over the crisis in Flint, they themselves have failed to offer proper support. Adjusted for inflation, the EPA's drinking water office budget has fallen 15 percent since 2006, and the agency has lost more than a tenth of its staff. States have also been left without desperately needed funds. In 2013, the Association of State Drinking Water Administrators said that federal officials had cut drinking water grants and 17 states had slashed drinking water budgets by more than 20 percent.

Lack of funding is not the only issue. Millions are at risk of unsafe drinking water because the drinking water enforcement systems in many states do not subject small utilities to the same safety rules as everyone else.

In fact, tiny utilities that serve only several thousand people or less often do not have to treat water to prevent lead contamination until after lead has been discovered. Even when they miss safety tests or do not treat water after they find lead, federal and state regulators often fail to make them comply with the law.

This has essentially created a two-tier regulatory system in law and practice, where poor, remote and rural communities are most likely to suffer the effects of inadequate safety measures and unjustly left exposed to lead poisoning.

But these aren't the only reasons why millions of Americans have been poisoned over the past few decades. Corporate interests have, as always, played their own role.

In Corpus Christi, for instance, a Mississippi-based company was responsible for a spill that poisoned the city's water with an asphalt emulsifier that can burn human skin in concentrated form. According to officials, Ergon Asphalt and Emulsion Inc. released 24 gallons of the contaminant after a "back-flow incident" in the city's industrial district. About 320,000 people had to be warned to avoid even touching their tap water until the crisis is resolved.

In another example, more than 80,000 Pittsburgh residents found out last summer that they had been exposed to high levels of lead through their drinking water. The culprit, according to the city government, was Veolia, a Paris-based company that consults or manages water, waste and energy systems in cities around the world. The Pittsburgh Water and Sewer Authority hired Veolia to help the city meet the challenge of making ends meet with shrinking public funding and increasingly outmoded infrastructure. In the end, Veolia allegedly became overly zealous with its cost-cutting measures, prioritizing cost savings rather than effective corrosion control methods, adequate staffing or water safety.

Pittsburgh is one of several communities where the company's business practices have ended up hurting residents, both in Europe and here in the US. For example, after Veolia-controlled Vilniaus Energija secured responsibility for the heating infrastructure of Vilnius and nine other cities in Lithuania in 2002, it manipulated prices in the Lithuanian market in order to unlawfully increase heating costs and therefore its profits by roughly $25 million - taking advantage of the fact that 90 percent of Vilnius' population relies on the company for heating. Closer to home, Veolia's North American subsidiary had a direct role to play in the Flint scandal. Michigan's attorney general is now suing the company for ignoring the risk of lead contamination in its review of the city's water supply.

Thanks to poor funding, gaps in oversight and letting corporate interests drive policy, millions of Americans are being exposed to lead and other substances in their drinking water through no fault of their own. This is nothing less than a national tragedy, and it will take nothing less than a fundamental rethink of how our country provides its most basic services to make sure nothing like this happens again.

Thousands of Americans drink tap water poisoned by unsafe levels of a cancer-causing heavy metal, and government authorities are doing little to stop it, according to a new report from clean water activists.

The chemical hexavalent chromium, also known as chromium-6, gained notoriety as the carcinogenic water contaminant that Erin Brockovich sued a utility over in California—and the new report from advocacy organization Environmental Working Group finds that it shows up in the water systems of major cities all over the country.

The data estimate that water supplies serving 218 million Americans—more than two-thirds of the population—contain more chromium-6 than California scientists have deemed safe. The group estimated that if nothing changes, chromium-6 in tap water will lead to more than 12,000 excess cases of cancer by the end of the century.

The findings are one more sign of a broken state and federal regulatory system that enabled crises in Flint, Michigan, and Hoosick Falls, New York, among other cities where dangerous contaminants in tap water threatened public health, advocates say.

"This is a repeating story of the lack of regulatory oversight and scientific updates to ensure clean drinking water," Bill Walker, a coauthor of the report, told TakePart. "A basic aspect of public health is being able to drink the tap water. We have not achieved that in the U.S."